The sign in question is posted on the side of a parked bus, and reads: 'Only a REAL INDIAN can defeat the fake Indian.' It also shows a picture of both candidates — the Bombay-born Ayyadurai in a suit, and Senator Warren shown wearing a photo-shopped Native American headdress.

In early April, Cambridge building inspector Branden Vigneault sent a notice to Ayyadurai's campaign saying that the sign must be removed since it lacked the necessary "approvals and permits." Fines imposed for keeping the sign up could be $300 per day, plus other fees.

But the candidate argues that since the sign is posted on a vehicle in front of a building that he owns, he is violating no ordinances. Ayyadurai said, "We will not remove the slogan from our bus. We will defend the First Amendment, and we will fight this egregious attack on the First Amendment, at any cost."

Ayyudurai is an Independent candidate who is seen as a long shot in his challenge against Warren.

Senator Warren has taken considerable heat for claiming to be a "woman of color" with Native American heritage, but has refused to verify any tribal lineage. Last month, she turned down a columnist's request to take a DNA test to confirm her roots. But Warren said she would rather rely on what she had been told by family, saying of her story, "It's a part of me, and nobody's going to take that part of me away."

Cherokee genealogist Twila Barnes researched Warren's history, and later wrote that "The problem with Warren's story is that none of the evidence supports it."

President Trump has repeatedly referred to Senator Warren as "Pocahontas," mocking her invalidated claims. At one point, she entertained the idea of running against the President in 2020, but has since said she would not be making a run for the White House.